Lexmark C540 Service Manual - Page 75

5025-2xx, 4xx Operator panel display is dim and unchanging Step Questions / actions Yes No 1 Turn the printer off, and remove the rear shield. See "Rear shield removal" on page 4-11. Turn the printer on, and verify the following values at JOPP1 on the controller board: JOPP1 Pin Value 1 0 V dc 2 +5 V dc 3 0 V dc 4 Ground 5 +5 V dc 6 +3.3 V dc 7 Ground Are all these values approximately correct? 2 Check for continuity in the operator panel cable connector. Note: Remove the three screws holding the operator panel, and place it facedown on top of the printer. The cable connector pins will be exposed and easier to contact. Do all the conductors indicate continuity? Go to step 2. Replace the operator panel. See "Operator panel removal" on page 4-9. Replace the controller board. See "Controller board removal" on page 4-19. Replace the front cover assembly. See "Front cover assembly removal" on page 4-2. Diagnostic information 2-41